Reduction of oxides of nitrogen in a gas stream using molecular sieve SSZ-70

ABSTRACT

The present invention relates to new crystalline molecular sieve SSZ-70 prepared using a N,N′-diisopropyl imidazolium cation as a structure-directing agent, methods for synthesizing SSZ-70 and processes employing SSZ-70 in a catalyst.

This application claims benefit under 35 USC 119 of ProvisionalApplication 60/639,218, filed Dec. 23, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to new crystalline molecular sieve SSZ-70,a method for preparing SSZ-70 using a N,N′-diisopropyl imidazoliumcation as a structure directing agent and the use of SSZ-70 in catalystsfor the reduction of oxides of nitrogen in a gas stream.

2. State of the Art

Because of their unique sieving characteristics, as well as theircatalytic properties, crystalline molecular sieves and zeolites areespecially useful in applications such as hydrocarbon conversion, gasdrying and separation. Although many different crystalline molecularsieves have been disclosed, there is a continuing need for new zeoliteswith desirable properties for gas separation and drying, hydrocarbon andchemical conversions, and other applications. New zeolites may containnovel internal pore architectures, providing enhanced selectivities inthese processes.

Crystalline aluminosilicates are usually prepared from aqueous reactionmixtures containing alkali or alkaline earth metal oxides, silica, andalumina. Crystalline borosilicates are usually prepared under similarreaction conditions except that boron is used in place of aluminum. Byvarying the synthesis conditions and the composition of the reactionmixture, different zeolites can often be formed.

SUMMARY OF THE INVENTION

The present invention is directed to a family of crystalline molecularsieves with unique properties, referred to herein as “molecular sieveSSZ-70” or simply “SSZ-70”. Preferably, SSZ-70 is obtained in itssilicate, aluminosilicate, titanosilicate, vanadosilicate orborosilicate form. The term “silicate” refers to a molecular sievehaving a high mole ratio of silicon oxide relative to aluminum oxide,preferably a mole ratio greater than 100, including molecular sievescomprised entirely of silicon oxide. As used herein, the term“aluminosilicate” refers to a molecular sieve containing both aluminumoxide and silicon oxide and the term “borosilicate” refers to amolecular sieve containing oxides of both boron and silicon. It shouldbe noted that the mole ratio of oxide (1) to oxide (2) can be infinity,i.e., there is no oxide (2) in the molecular sieve. In these cases, themolecular sieve is an essentially all-silica molecular sieve.

In accordance with this invention, provided a process for the reductionof oxides of nitrogen contained in a gas stream in the presence ofoxygen wherein said process comprises contacting the gas stream with amolecular sieve, the molecular sieve having a mole ratio greater thanabout 15 of (1) silicon oxide to (2) an oxide selected from aluminumoxide, gallium oxide, iron oxide, boron oxide, titanium oxide, vanadiumoxide and mixtures thereof, and having, after calcination, the X-raydiffraction lines of Table II. The molecular sieve may contain a metalor metal ions (such as cobalt, copper, platinum, iron, chromium,manganese, nickel, zinc, lanthanum, palladium, rhodium or mixturesthereof) capable of catalyzing the reduction of the oxides of nitrogen,and the process may be conducted in the presence of a stoichiometricexcess of oxygen. In a preferred embodiment, the gas stream is theexhaust stream of an internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an X-ray diffraction pattern of SSZ-70 after it has beencalcined.

FIG. 2 is an X-ray diffraction pattern of SSZ-70 in the as-synthesizedform, i.e., prior to calcination with the SDA still in the pores of theSSZ-70.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a family of crystalline molecular sievesdesignated herein “molecular sieve SSZ-70” or simply “SSZ-70”. Inpreparing SSZ-70, a N,N′-diisopropyl imidazolium cation (referred toherein as “DIPI”) is used as a structure directing agent (“SDA”), alsoknown as a crystallization template. The SDA useful for making SSZ-70has the following structure:

The SDA cation is associated with an anion (X⁻) which may be any anionthat is not detrimental to the formation of the molecular sieve.Representative anions include halogen, e.g., fluoride, chloride, bromideand iodide, hydroxide, acetate, sulfate, tetrafluoroborate, carboxylate,and the like. Hydroxide is the most preferred anion.

SSZ-70 is prepared from a reaction mixture having the composition shownin Table A below.

TABLE A Reaction Mixture Typical Preferred YO₂/B₂O₃  5–60 10–60 OH—/YO₂0.10–0.50 0.20–0.30 Q/YO₂ 0.05–0.50 0.10–0.20 M_(2/n)/YO₂   0–0.400.10–0.25 H₂O/YO₂ 30–80 35–45 F/YO₂   0–0.50 0where Y is silicon; M is an alkali metal cation, alkaline earth metalcation or mixtures thereof; n is the valence of M (i.e., 1 or 2); F isfluorine and Q is a N,N′-diisopropyl imidazolium cation.

In practice, SSZ-70 is prepared by a process comprising:

(a) preparing an aqueous solution containing sources of at least twooxides capable of forming a crystalline molecular sieve and a DIPIcation having an anionic counterion which is not detrimental to theformation of SSZ-70;

(b) maintaining the aqueous solution under conditions sufficient to formcrystals of SSZ-70; and

(c) recovering the crystals of SSZ-70.

Accordingly, SSZ-70 may comprise the crystalline material and the SDA incombination with metallic and non-metallic oxides bonded in tetrahedralcoordination through shared oxygen atoms to form a cross-linked threedimensional crystal structure. Typical sources of silicon oxide includesilicates, silica hydrogel, silicic acid, fumed silica, colloidalsilica, tetra-alkyl orthosilicates, and silica hydroxides. Boron can beadded in forms corresponding to its silicon counterpart, such as boricacid.

A source zeolite reagent may provide a source of boron. In most cases,the source zeolite also provides a source of silica. The source zeolitein its deboronated form may also be used as a source of silica, withadditional silicon added using, for example, the conventional sourceslisted above. Use of a source zeolite reagent for the present process ismore completely described in U.S. Pat. No. 5,225,179, issued Jul. 6,1993 to Nakagawa entitled “Method of Making Molecular Sieves”, thedisclosure of which is incorporated herein by reference.

Typically, an alkali metal hydroxide and/or an alkaline earth metalhydroxide, such as the hydroxide of sodium, potassium, lithium, cesium,rubidium, calcium, and magnesium, is used in the reaction mixture;however, this component can be omitted so long as the equivalentbasicity is maintained. The SDA may be used to provide hydroxide ion.Thus, it may be beneficial to ion exchange, for example, the halide tohydroxide ion, thereby reducing or eliminating the alkali metalhydroxide quantity required. The alkali metal cation or alkaline earthcation may be part of the as-synthesized crystalline oxide material, inorder to balance valence electron charges therein.

The reaction may also be carried out using HF to counterbalance theOH-contribution from the SDA, and run the synthesis in the absence ofalkali cations. Running in the absence of alkali cations has theadvantage of being able to prepare a catalyst from the synthesisproduct, by using calcination alone, i.e., no ion-exchange step (toremove alkali or alkaline earth cations) is necessary. In using HF, thereaction operates best when both the SDA and HF have mole ratios of 0.50relative to YO₂ (e.g., silica).

The reaction mixture is maintained at an elevated temperature until thecrystals of the SSZ-70 are formed. The hydrothermal crystallization isusually conducted under autogenous pressure, at a temperature between100° C. and 200° C., preferably between 135° C. and 160° C. Thecrystallization period is typically greater than 1 day and preferablyfrom about 3 days to about 20 days.

Preferably, the molecular sieve is prepared using mild stirring oragitation.

During the hydrothermal crystallization step, the SSZ-70 crystals can beallowed to nucleate spontaneously from the reaction mixture. The use ofSSZ-70 crystals as seed material can be advantageous in decreasing thetime necessary for complete crystallization to occur. In addition,seeding can lead to an increased purity of the product obtained bypromoting the nucleation and/or formation of SSZ-70 over any undesiredphases. When used as seeds, SSZ-70 crystals are added in an amountbetween 0.1 and 10% of the weight of first tetravalent element oxide,e.g. silica, used in the reaction mixture.

Once the molecular sieve crystals have formed, the solid product isseparated from the reaction mixture by standard mechanical separationtechniques such as filtration. The crystals are water-washed and thendried, e.g., at 90° C. to 150° C. for from 8 to 24 hours, to obtain theas-synthesized SSZ-70 crystals. The drying step can be performed atatmospheric pressure or under vacuum.

SSZ-70 as prepared has a mole ratio of (1) silicon oxide to (2) boronoxide greater than about 15; and has, after calcination, the X-raydiffraction lines of Table II below. SSZ-70 further has a composition,as synthesized (i.e., prior to removal of the SDA from the SSZ-70) andin the anhydrous state, in terms of mole ratios, shown in Table B below.

TABLE B As-Synthesized SSZ-70 YO₂/B₂O₃ 20–60 M_(2/n)/YO₂   0–0.03 Q/YO₂0.02–0.05 F/YO₂   0–0.10where Y, M, n and Q are as defined above.

SSZ-70 can be an essentially all-silica material. As used herein,“essentially all-silica” means that the molecular sieve is comprised ofonly silicon oxide or is comprised of silicon oxide and only traceamounts of other oxides, such as aluminum oxide, which may be introducedas impurities in the source of silicon oxide. Thus, in a typical casewhere oxides of silicon and boron are used, SSZ-70 can be madeessentially boron free, i.e., having a silica to boron oxide mole ratioof ∞. SSZ-70 is made as a borosilicate and then the boron can then beremoved, if desired, by treating the borosilicate SSZ-70 with aceticacid at elevated temperature (as described in Jones et al., Chem.Mater., 2001, 13, 1041-1050) to produce an essentially all-silicaversion of SSZ-70.

If desired, SSZ-70 can be made as a borosilicate and then the boron canbe removed as described above and replaced with metal atoms bytechniques known in the art. Aluminum, gallium, iron, titanium, vanadiumand mixtures thereof can be added in this manner.

It is believed that SSZ-70 is comprised of a new framework structure ortopology which is characterized by its X-ray diffraction pattern.SSZ-70, as-synthesized, has a crystalline structure whose X-ray powderdiffraction pattern exhibit the characteristic lines shown in Table Iand is thereby distinguished from other molecular sieves.

TABLE I As-Synthesized SSZ-70 2 Theta^((a)) d-spacing (Angstroms)Relative Intensity (%)^((b)) 3.32 26.6 VS 6.70 13.2 VS 7.26 12.2 S 8.7810.1 S 13.34 6.64 M 20.02 4.44 S 22.54 3.94 M 22.88 3.89 M 26.36 3.38S-VS 26.88 3.32 M ^((a))± 0.15 ^((b))The X-ray patterns provided arebased on a relative intensity scale in which the strongest line in theX-ray pattern is assigned a value of 100: W(weak) is less than 20;M(medium) is between 20 and 40; S(strong) is between 40 and 60; VS(verystrong) is greater than 60.Table IA below shows the X-ray powder diffraction lines foras-synthesized SSZ-70 including actual relative intensities.

TABLE IA 2 Theta^((a)) d-spacing (Angstroms) Relative Intensity (%) 3.3226.6 84 6.70 13.2 100 7.26 12.2 45 8.78 10.1 44 13.34 6.64 26 20.02 4.4446 22.54 3.94 33 22.88 3.89 36 26.36 3.38 61 26.88 3.32 31 ^((a))± 0.15

After calcination, the SSZ-70 molecular sieves have a crystallinestructure whose X-ray powder diffraction pattern include thecharacteristic lines shown in Table II:

TABLE II Calcined SSZ-70 2 Theta^((a)) d-spacing (Angstroms) RelativeIntensity (%) 7.31 12.1 VS 7.75 11.4 VS 9.25 9.6 VS 14.56 6.08 VS 15.615.68 S 19.60 4.53 S 21.81 4.07 M 22.24 4.00 M-S 26.30 3.39 VS 26.81 3.33VS ^((a))± 0.15

Table IIA below shows the X-ray powder diffraction lines for calcinedSSZ-70 including actual relative intensities.

TABLE IIA 2 Theta^((a)) d-spacing (Angstroms) Relative Intensity (%)7.31 12.1 67 7.75 11.4 93 9.25 9.6 79 14.56 6.08 68 15.61 5.68 49 19.604.53 58 21.81 4.07 38 22.24 4.00 41 26.30 3.39 99 26.81 3.33 80 ^((a))±0.15

The X-ray powder diffraction patterns were determined by standardtechniques. The radiation was the K-alpha/doublet of copper. The peakheights and the positions, as a function of 2θ where θ is the Braggangle, were read from the relative intensities of the peaks, and d, theinterplanar spacing in Angstroms corresponding to the recorded lines,can be calculated.

The variation in the scattering angle (two theta) measurements, due toinstrument error and to differences between individual samples, isestimated at ±0.15 degrees.

The X-ray diffraction pattern of Table I is representative of“as-synthesized” or “as-made” SSZ-70 molecular sieves. Minor variationsin the diffraction pattern can result from variations in thesilica-to-boron mole ratio of the particular sample due to changes inlattice constants. In addition, sufficiently small crystals will affectthe shape and intensity of peaks, leading to significant peakbroadening.

Representative peaks from the X-ray diffraction pattern of calcinedSSZ-70 are shown in Table II. Calcination can also result in changes inthe intensities of the peaks as compared to patterns of the “as-made”material, as well as minor shifts in the diffraction pattern. Themolecular sieve produced by exchanging the metal or other cationspresent in the molecular sieve with various other cations (such as H⁺ orNH₄ ⁺) yields essentially the same diffraction pattern, although again,there may be minor shifts in the interplanar spacing and variations inthe relative intensities of the peaks. Notwithstanding these minorperturbations, the basic crystal lattice remains unchanged by thesetreatments.

Crystalline SSZ-70 can be used as-synthesized, but preferably will bethermally treated (calcined). Usually, it is desirable to remove thealkali metal cation by ion exchange and replace it with hydrogen,ammonium, or any desired metal ion. The molecular sieve can be leachedwith chelating agents, e.g., EDTA or dilute acid solutions, to increasethe silica to alumina mole ratio. The molecular sieve can also besteamed; steaming helps stabilize the crystalline lattice to attack fromacids.

The molecular sieve can be used in intimate combination withhydrogenating components, such as tungsten, vanadium, molybdenum,rhenium, nickel, cobalt, chromium, manganese, or a noble metal, such aspalladium or platinum, for those applications in which ahydrogenation-dehydrogenation function is desired.

Metals may also be introduced into the molecular sieve by replacing someof the cations in the molecular sieve with metal cations via standardion exchange techniques (see, for example, U.S. Pat. Nos. 3,140,249issued Jul. 7, 1964 to Plank et al.; U.S. Pat. No. 3,140,251 issued Jul.7, 1964 to Plank et al.; and U.S. Pat. No. 3,140,253 issued Jul. 7, 1964to Plank et al.). Typical replacing cations can include metal cations,e.g., rare earth, Group IA, Group IIA and Group VIII metals, as well astheir mixtures. Of the replacing metallic cations, cations of metalssuch as rare earth, Mn, Ca, Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, andFe are particularly preferred.

The hydrogen, ammonium, and metal components can be ion-exchanged intothe SSZ-70. The SSZ-70 can also be impregnated with the metals, or themetals can be physically and intimately admixed with the SSZ-70 usingstandard methods known to the art.

Typical ion-exchange techniques involve contacting the syntheticmolecular sieve with a solution containing a salt of the desiredreplacing cation or cations. Although a wide variety of salts can beemployed, chlorides and other halides, acetates, nitrates, and sulfatesare particularly preferred. The molecular sieve is usually calcinedprior to the ion-exchange procedure to remove the organic matter presentin the channels and on the surface, since this results in a moreeffective ion exchange. Representative ion exchange techniques aredisclosed in a wide variety of patents including U.S. Pat. No. 3,140,249issued on Jul. 7, 1964 to Plank et al.; U.S. Pat. No. 3,140,251 issuedon Jul. 7, 1964 to Plank et al.; and U.S. Pat. No. 3,140,253 issued onJul. 7, 1964 to Plank et al.

Following contact with the salt solution of the desired replacingcation, the molecular sieve is typically washed with water and dried attemperatures ranging from 65° C. to about 200° C. After washing, themolecular sieve can be calcined in air or inert gas at temperaturesranging from about 200° C. to about 800° C. for periods of time rangingfrom 1 to 48 hours, or more, to produce a catalytically active productespecially useful in hydrocarbon conversion processes.

Regardless of the cations present in the synthesized form of SSZ-70, thespatial arrangement of the atoms which form the basic crystal lattice ofthe molecular sieve remains essentially unchanged.

SSZ-70 can be formed into a wide variety of physical shapes. Generallyspeaking, the molecular sieve can be in the form of a powder, a granule,or a molded product, such as extrudate having a particle size sufficientto pass through a 2-mesh (Tyler) screen and be retained on a 400-mesh(Tyler) screen. In cases where the catalyst is molded, such as byextrusion with an organic binder, the SSZ-70 can be extruded beforedrying, or, dried or partially dried and then extruded.

SSZ-70 can be composited with other materials resistant to thetemperatures and other conditions employed in organic conversionprocesses. Such matrix materials include active and inactive materialsand synthetic or naturally occurring zeolites as well as inorganicmaterials such as clays, silica and metal oxides. Examples of suchmaterials and the manner in which they can be used are disclosed in U.S.Pat. No. 4,910,006, issued May 20, 1990 to Zones et al., and U.S. Pat.No. 5,316,753, issued May 31, 1994 to Nakagawa, both of which areincorporated by reference herein in their entirety.

SSZ-70 may be used for the catalytic reduction of the oxides of nitrogenin a gas stream. Typically, the gas stream also contains oxygen, often astoichiometric excess thereof. Also, the SSZ-70 may contain a metal ormetal ions within or on it which are capable of catalyzing the reductionof the nitrogen oxides. Examples of such metals or metal ions includecobalt, copper, platinum, iron, chromium, manganese, nickel, zinc,lanthanum, palladium, rhodium and mixtures thereof.

One example of such a process for the catalytic reduction of oxides ofnitrogen in the presence of a zeolite is disclosed in U.S. Pat. No.4,297,328, issued Oct. 27, 1981 to Ritscher et al., which isincorporated by reference herein. There, the catalytic process is thecombustion of carbon monoxide and hydrocarbons and the catalyticreduction of the oxides of nitrogen contained in a gas stream, such asthe exhaust gas from an internal combustion engine. The zeolite used ismetal ion-exchanged, doped or loaded sufficiently so as to provide aneffective amount of catalytic copper metal or copper ions within or onthe zeolite. In addition, the process is conducted in an excess ofoxidant, e.g., oxygen.

EXAMPLES

The following examples demonstrate but do not limit the presentinvention.

Examples 1-6 Synthesis of Borosilicate SSZ-70 (B-SSZ-70)

B-SSZ-70 is synthesized by preparing the gel compositions, i.e.,reaction mixtures, having the compositions, in terms of mole ratios,shown in the table below. The resulting gel is placed in a Parr bombreactor and heated in an oven at the temperature (° C.) indicated in thetable while rotating at 43 rpm. Amounts in the table are in millimoles.Products are analyzed by X-ray diffraction (XRD) and found to beB-SSZ-70 or a mixture of B-SSZ-70 and amorphous material.

Ex. No. SiO₂ DIPI H₂O/SiO₂ HF H₃BO₃ Temp., ° C. Seeds Days Prod. 1 18 915 9 1.0 150 No 95 AM/B-SSZ-70 2 18 9 15 9 1.0 150 Yes 98 AM/B-SSZ-70 318 9 15 9 1.0 170 No 52 B-SSZ-70 4 18 9 15 9 1.0 150 Yes 80 B-SSZ-70 518 9 15 9 3.3 170 No 52 B-SSZ-70 6 18 9 15 9 5.0 170 No 61 B-SSZ-70 AM =amorphous material

The X-ray diffraction lines for as-synthesized SSZ-70 are shown in thetable below.

As-Synthesized SSZ-70 XRD 2 Theta^((a)) d-spacing (Angstroms) RelativeIntensity (%) 3.32 26.6 84 6.70 13.2 100 7.26 12.2 45 8.78 10.1 44 10.048.81 20 10.88 8.13 17 13.00 6.81 16 13.34 6.64 26 14.60 6.07 23 15.365.77 14 16.66 5.32 10 18.54 4.79 6 19.30 4.60 14 20.02 4.44 46 21.864.07 25 22.54 3.94 33 22.88 3.89 36 24.38 3.65 13 25.28 3.52 25 26.363.38 61 26.88 3.32 31 29.56 3.02 6 32.00 2.80 8 33.61 2.67 4 36.94 2.435 38.40 2.34 7 ^((a))± 0.15

Example 7

A run is set up as in the table above but the mole ratios are asfollows: SiO₂=16 mmoles, DIPI=5 mmoles, H₃BO₃=4 mmoles and water=240mmoles. No HF component is used. The reaction is run for only seven daysat 43 RPM at 170° C. The product is SSZ-70.

Example 8 Calcination of SSZ-70

SSZ-70 is calcined to remove the structure directing agent (SDA) asdescribed below. A thin bed of SSZ-70 in a calcination dish is heated ina muffle furnace from room temperature to 120° C. at a rate of 1°C./minute and held for 2 hours. Then, the temperature is ramped up to540° C. at a rate of 1° C./minute and held for 5 hours. The temperatureis ramped up again at 1° C./minute to 595° C. and held there for 5hours. A 50/50 mixture of air and nitrogen passes through the mufflefurnace at a rate of 20 standard cubic feet (0.57 standard cubic meters)per minute during the calcination process. The XRD lines for calcinedSSZ-70 are shown in the table below.

2 Theta^((a)) d-spacing (Angstroms) Relative Intensity (%) 3.93 22.5 227.31 12.1 67 7.75 11.4 93 9.25 9.6 79 14.56 6.08 68 15.61 5.68 49 17.345.11 15 19.60 4.53 58 21.81 4.07 38 22.24 4.00 41 23.11 3.85 77 25.303.52 23 26.30 3.39 99 26.81 3.33 80 ^((a))± 0.15

Example 9 Replacement of Boron with Aluminum

Calcined SSZ-70 (about 5 grams) is combined with 500 grams of 1 Maqueous Al(NO₃)₃ solution and treated under reflux for 100 hours. Theresulting aluminum-containing SSZ-70 product is then washed with 100 ml0.01N HCl and then with one liter of water, filtered and air dried atroom temperature in a vacuum filter.

Example 10 Constraint Index

The hydrogen form of calcined SSZ-70 is pelletized at 3 KPSI, crushedand granulated to 20-40 mesh. A 0.6 gram sample of the granulatedmaterial is calcined in air at 540° C. for 4 hours and cooled in adesiccator to ensure dryness. Then, 0.5 gram is packed into a ⅜ inchstainless steel tube with alundum on both sides of the molecular sievebed. A Lindburg furnace is used to heat the reactor tube. Helium isintroduced into the reactor tube at 10 cc/min. and at atmosphericpressure. The reactor is heated to about 427° C. (800° F.), and a 50/50feed of n-hexane and 3-methylpentane is introduced into the reactor at arate of 8 μl/min. The feed is delivered by a Brownlee pump. Directsampling into a GC begins after 10 minutes of feed introduction. TheConstraint Index (CI) value is calculated from the GC data using methodsknown in the art. The results are shown in the table below.

Time, Min. 10 40 70 100 Feed Conv. % 6.4 6.5 6.5 6.4 CI (excl. 2- 0.60.59 0.56 0.56 MP) CI (incl. 2-MP) 0.78 0.79 0.75 0.76 2-MP =2-methylpentane

Example 11 Hydrocracking of n-Hexadecane

A 1 gm sample of calcined SSZ-70 is suspended in 10 gm de-ionized water.To this suspension, a solution of Pt(NH₃)₄.(NO₃)₂ at a concentrationwhich would provide 0.5 wt. % Pt with respect to the dry weight of themolecular sieve sample is added. The pH of the solution is adjusted topH of ˜9 by a drop-wise addition of dilute ammonium hydroxide solution.The mixture is then allowed to stand at 25° C. for 48 hours. The mixtureis then filtered through a glass frit, washed with de-ionized water, andair-dried. The collected Pt-SSZ-70 sample is slowly calcined up to 288°C. in air and held there for three hours.

The calcined Pt/SSZ-70 catalyst is pelletized in a Carver Press andgranulated to yield particles with a 20/40 mesh size. Sized catalyst(0.5 g) is packed into a ¼ inch OD tubing reactor in a micro unit forn-hexadecane hydroconversion. The table below gives the run conditionsand the products data for the hydrocracking test on n-hexadecane.

The results shown in the table below show that SSZ-70 is effective as ahydrocracking catalyst. The data show that the catalyst has a very highselectivity for hydrocracking to linear paraffins, rather thanisomerization selectivity. Also, a high ratio of liquid/gas (C₅₊/C⁴⁻) isachieved.

Temperature 660° F. (349° C.) 690° F. (366° C.) Time-on-Stream (hrs.) 40hours 53 hours PSIG 2200 2200 Titrated? No No n-16, % Conversion 52% 89%Isomerization Selectivity, % 5.1 2.2 C₅₊/C⁴⁻ 11.5 7.0 C₄–C₁₃ i/n 0.020.03

Example 12 Micropore Volume

SSZ-70 has a micropore volume of 0.071 cc/gm based on argon adsorptionisotherm at 87.5° K. (−186° C.) recorded on ASAP 2010 equipment fromMicromerities. The sample is first degassed at 400° C. for 16 hoursprior to argon adsorption. The low-pressure dose is 2.00 cm³/g (STP). Amaximum of one hour equilibration time per dose is used and the totalrun time is 37 hours. The argon adsorption isotherm is analyzed usingthe density function theory (DFT) formalism and parameters developed foractivated carbon slits by Olivier (Porous Mater. 1995, 2, 9) using theSaito Foley adaptation of the Horvarth-Kawazoe formalism (MicroporousMaterials, 1995, 3, 531) and the conventional t-plot method (J.Catalysis, 1965, 4, 319) (micropore volume by the t-plot method is 0.074cc/gm).

1. A process for the reduction of oxides of nitrogen contained in a gasstream wherein said process comprises contacting the gas stream with amolecular sieve, the molecular sieve having a mole ratio greater thanabout 15 of (1) silicon oxide to (2) an oxide selected from aluminumoxide, gallium oxide, iron oxide, boron oxide, titanium oxide, vanadiumoxide and mixtures thereof and having, after calcination, the X-raydiffraction lines of Table II.
 2. The process of claim 1 conducted inthe presence of oxygen.
 3. The process of claim 1 wherein said molecularsieve contains a metal or metal ions capable of catalyzing the reductionof the oxides of nitrogen.
 4. The process of claim 3 wherein the metalis cobalt, copper, platinum, iron, chromium, manganese, nickel, zinc,lanthanum, palladium, rhodium or mixtures thereof.
 5. The process ofclaim 1 wherein the gas stream is the exhaust stream of an internalcombustion engine.
 6. The process of claim 4 wherein the gas stream isthe exhaust stream of an internal combustion engine.